# delete node from doubly link list
#singleton class for multithreading system
#write code stack class which also gives max item
#design pattern - observer, factory, decorator
#difference tcp udp. Blocking and non blocking port.
#sip call from.. How many requests create call leg? Refer and subscribe...dialogue, transaction for 200 OK and non 200 response.
#http and sip
#c++ template, virtual table, up and down cast, double free, modify read only string, how to initialize reference variable of class, bitwise operator - 1s compliment, or, left and right shift, sizeof operator for 64 bits, exception, virtual destructor, abstract class instantiation